[11] Multiple Pregnancy Flashcards
What is a multiple pregnancy?
A pregnancy with twins, triplets, or higher numbers of embryos
Why is multiple pregnancy considered to be high risk?
Due to the increased risk of maternal and fetal morbidity and mortality
Give 2 factors that cause variation in the prevalence of multiple pregnancy
- Race
- Use of reproductive techniques
What is the rate of twin births in North America and Europe?
5-13 twin sets per 1000 live births
What has recently happened to the rate of twin pregnancies?
Rapidly increased
Why has there recently been a rapid increase in number of twin pregnancies?
Due to reproductive technology, resulting from ovulation induction and replacement of more than one fertilised embryo in the IVF cycle
What changes have been make to reproductive technologies as a result of the risks of multiple pregnancies?
The technique of replacing many embryos to enhance conception rates has been abandoned, resulting in a fall in the rates of twins
What is monozygotic multiple pregnancy also known as?
Uniovular, or identical
When does monozygotic twin pregnancy occur?
When a single ova results in multiple embryos
What is the rate of monozygotic twin pregnancy?
1/280 pregnancies
What happens in the formation of a monozygotic pregnancy?
The zygote divides sometime after conception
What is the importance of the time of split in monozygotic twin pregnancies?
The time of split determines the features of the embryos
What happens if the zygote splits after 0-4 days in monozygotic pregnancies?
There will be 2 embyros, 2 amnions, and 2 chorions
What % of monozygotic pregnancies split after 0-4 days?
25-30%
What happens if the zygote splits after 4-8 days in monozygotic pregnancies?
There will be 2 embryos, 2 amnions, and 1 chorion
What % of monozygotic pregnancies split after 4-8 days?
65-70%
What happens if the zygote splits after 9-12 days in monozygotic pregnancies?
There will be 2 embryos, 1 amnion, and 1 chorion
What % of monozygotic pregnancies split after 9-12 days?
1-2%
What happens if the zygote splits after 13+ days in monozygotic pregnancies?
There will be conjoint twins, 1 amnion, and 1 chorion
What % of monozygotic pregnancies split after 13+ days?
<1%
What happens if the embryo splits into 3?
Get monozygotic triplets
Does the splitting of the embryo in monozygotic triplets occur at the same time or sequentially?
Can be either
How is the determination of monozygosity performed?
By ultrasound
When should determination of monozygosity by ultrasound occur?
Preferably before 14 weeks
What will a pregnancy where the embryo split after 4 days show on ultrasound?
A single thin membrane or no membrane, and a single placental mass
What is it called when a pregnancy where the embryo split after 4 days has a single thin membrane?
Monochorionic diamniotic
What is it called when a pregnancy where the embryo split after 4 days has no membrane?
Monochorionic monoamniotic
What will a pregnancy where the embryo split before 4 days show on ultrasound?
There may be 2 separate placental masses, or a single mass with a twin peak sign where the membranes and placenta intersect
Why is early determination of zygosity important?
In order to plan the management of the pregnancy
Other than ultrasound, what can be used to confirm zygosity?
Genetic assessment of amniotic fluid, chorionic villus sampling, or postnatal cord blood
Why is confirmation of zygosity by means other than ultrasound rarely used?
Due to modern ultrasound technology
When does dizygotic multiple pregnancies occur?
When there is separate fertilisation of separate ova by different sperm
What does dizygotic multiple pregnancies produce?
Non-identical twins
What will be found on ultrasound in dizygotic twin pregnancies?
2 separate placentas on ultrasound, or a single placenta with a twin peak sign
What signs can be useful in the determining if a twin pregnancy is monochorionic diamniotic or dichorionic diamniotic twins?
Lambda and T sign
What is lambda sign?
Chorion in between the membranes at the site of membrane insertion of the placenta
What is T sign?
Absence of chorion between the membranes at the site of membrane insertion of the placenta
What does lambda sign indicate?
Dichorionic diamniotic twins
Why is important to differentiate between monochorionic diamniotic and dichorionic diamniotic twins?
Because monochorionic diamniotic twins may have placental vascular anastomosis
What might placental vascular anastomosis give rise to?
Twin-to-twin transfusion and its effects
What causes variation in the rate of dizygotic twins?
- Familial factors
- Parity
- Older mothers
- Ovulation induction
Do familial factors affect the rate of dizygotic pregnancies if they are on the mothers or fathers side?
Appears to be maternal side only
What effect does parity have on the rate of dizygotic twins?
Rate is higher with higher parity
What effect does maternal age have on the rate of dizygotic twins?
Small increase in older mothers
What can the use of gonadotrophin therapy result in?
Twins, triplets, or even higher order pregnancies
How can the use of gonadotrophin therapy leading to multiple pregnancy be avoided to some degree?
By monitoring ovarian follicular development and withholding injection of hCG if excessive number of follicles development
What happens to the normal processes of maternal physiological adaptation in multiple pregnancy?
They are exaggerated
Give 3 maternal physiological adaptations that are exaggerated in pregnancy
- Weight gain
- Increase in red cell mass
- Increased maternal cardiac output
How does weight gain differ in single vs multiple pregnancy?
On average, 3.5kg more in multiple pregnancy
What is the problem with the increase in red cell mass in multiple pregnancy?
It does not match the additional expansion in plasma volume compared to single pregnancy
What is the result of the expansion of red cell mass not matching the expansion of plasma volume in multiple pregnancy?
Relative anaemia develops
What complications are associated with all types of multiple pregnancy?
- Nausea and vomiting
- Anaemia
- Miscarriage
- Antepartum haemorrhage
- Gestational hypertension, pre-eclampsia, and eclampsia
- IUGR
- Pre-term labour
- Structural abnormalities
How does the nausea and vomiting compare in multiple pregnancy to single pregnancy?
It is early onset and increased severity in multiple pregnancy
How much more likely is the mother to develop anaemia in multiple pregnancy compared to single pregnancy?
2x
What should be done in women with multiple pregnancy to avoid anaemia?
As a minimum, all should consider iron and folate supplementation throughout gestation
In what % of twin pregnancies does resorption of the fetus occur?
15%
When can resorption of the fetus occur in twin pregnancies?
6-10 weeks
What it is called when there is resorption of one of the foetuses in twin pregnancies?
Vanishing twin syndrome
What kind of miscarriage has a higher incidence in twin pregnancies?
Threatened and actual
How much more likely is antepartum haemorrhage in multiple compared to single pregnancy?
2x
Why is there a higher risk of antepartum haemorrhage in multiple pregnancy?
Due to high risk of abruption and placenta praevia
How much more likely is pre-eclampsia in multiple compared to single pregnancies?
x3
How much more likely is eclampsia in multiple compared to single pregnancies?
x4
How much more likely is IUGR in multiple pregnancies compared to single pregnancies?
x3
In what % of twin pregnancies is one twin significantly smaller than the other?
20%
What is done as a result of the increased risk of IUGR in multiple pregnancies?
Regular ultrasound screening of growth and fetal wellbeing is mandatory
How much more likely is pre-term labour in multiple compared to single pregnancies?
6x
In what % of twin pregnancies does onset of labour before 37 weeks?
40%
What causes pre-term labour in multiple pregnancy?
Appears to be associated with over-distention of the uterus associated with presence of more than one fetus
What further increases the risk of pre-term labour in multiple pregnancy?
If amniotic fluid volume is increased
When in particular is there an increased risk of structural abnormalities in multiple pregnancy?
Monozygotic babies
What are the other complications of twin pregnancy associated with?
Zygosity
How does the rate of complications in monozygotic twins compare to dizygotic twins?
Higher
Why is there a higher rate of complications in monozygotic twins?
Due to the higher incidence of congenital abnormalities, pre-term delivery, and twin-to-twin transfusion syndrome
What complications are associated with monozygotic twin pregnancy?
- Twin-to-twin tranfusion syndrome
- Monoamnioticity
- Conjoined twinning
In what % of monochorionic diamniotic twin pregnancies does twin-to-twin transfusion syndrome arise in?
10-15%
What happens in twin-to-twin transfusion syndrome?
One fetus (the donor) transfuses the other (the recipient) through interlinked vascular channels in the placenta
When does twin-to-twin transfusion syndrome present?
In the second trimester
How does the donor twin present in twin-to-twin transfusion syndrome?
- Oliguric
- Growth restriction
- Oligohydraminos
How does the recipient fetus present in twin-to-twin transfusion syndrome?
- Polyhydraminos
- At risk of cardiomegaly and hydrops fetalis
What is the perinatal mortality of untreated twin-to-twin transfusion syndrome?
80%
What are the treatment options for twin-to-twin transfusion syndrome?
- Serial amniocentesis
- Selective feticide
- Laser ablation, via fetoscope, of communicating vessels
What happens in serial amniocentesis to treat twin-to-twin transfusion syndrome?
Removal of fluid around the recipient twin
What happens if one twin dies before laser ablation treatment in twin-to-twin transfusion syndrome?
The other twin often dies as a result of acute haemodynamic changes
In what % of monochorionic twins does monoamnioticity occur?
1%
What is a common complication in monoamniotic twins?
Cord entanglement by 22 weeks
Where does union occur in conjoined twinning?
Union can occur at any site, but most common are head-to-head or thorax-to-thorax
What does the prognosis for separation and normal life depend on in conjoined twins?
Site of fusion
How is the site of fusion determined in conjoined twins?
Tertiary level ultrasound by 18-20 weeks gestation
What happens when conjoined twins share a major cardiovascular connection or organ?
Perinatal death of at least 1 twin at separation is almost certain
What factors are important to determine in twin pregnancy?
- Pre-natal diagnosis
- Chronicity
- Assessment for impending TTTS
What is the most common clinical sign of twin pregnancy?
Greater size of uterus
What is the role of the increased size of the uterus as a clinical sign in twin pregnancy?
It is easier to detect in earlier pregnancy
Give 2 other reasons that the uterus may be enlarged?
- Hydraminos
- Uterine fibroids
How does the treatment of antenatal complications differ in twin pregnancies compared to single pregnancies?
It is the same as in single pregnancies, however it should be remembered that the onset of complications, particularly pre-term labour, tends to be earlier and of greater severity
What supervision is done in multiple pregnancy?
Careful antenatal supervision and ultrasound examinations done 2-4 weekly
What is the purpose of careful supervision and ultrasound examination in multiple pregnancy?
To detect fetal growth abnormality or TTTS
What should be done if IUGR is suspected with multiple pregnancy?
Early induction of labour should be considered
Why does delivery pose a difficulty in twin pregnancy?
Due to the variety and complexity of presentations, and because second twin is at significantly greater risk of asphyxia due to placental separation and cord prolapse/
What are the potential presentations for twin delivery?
- Cephalic/cephalic
- Cephalic/breech or breech/cephalic
- Breech/breech
- Other, e.g. transverse/cephalic, breech/transverse etc
What % of twin deliveries present cephalic/cephalic?
50%
What % of twin deliveries present cephalic/breech?
25%
What % of twin deliveries present breech/cephalic?
10%
What % of twin deliveries present breech/breech?
10%
When should the decision about the mode of delivery be made in twin pregnancy?
Ideally before the onset of labour
Describe the use of delivery by C-section in twin pregnancy
It is indicated for the same reasons as twin pregnancy, but the threshold is usually lower
What are the indications for C-section delivery in twin pregnancy?
- Additional complications
- Preterm labour between 28-34 weeks
- Malpresentation of first twin
What additional complications can indicate a C-section in twin pregnancy?
- Previous C-section scar
- Long history of subfertility
- Severe pre-eclampsia
How should higher order births, such as triplets or quadruplets, be delivered?
By C-section
What complications are often present with higher order births, such as triplets and quadruplets?
- Preterm labour
- Low birth weight
- Uncertain presentation
How does the time of labour for twin pregnancy compare to single pregnancy, if allowed to progress normally?
It usually lasts the same time
What should be done at an early stage if labour is allowed to progress normally for twin pregnancy?
Insertion of IV line
Why should an IV line be inserted at an early stage if labour for twin pregnancy is allowed to progress normally?
Because the delivery of the second baby can be complicated and require analgesia
How can the first baby be monitored during labour for twin pregnancy?
Scalp electrode or abdominal ultrasound
What should be done as soon as the first baby is delivered during labour in twin pregnancy?
The lie and presentation of the second twin must be immediately checked, and the fetal HR recorded
What should be done regarding the membranes during the delivery of the second twin in labour?
They should be left intact until the presenting part is well into the pelvis. If the baby is presenting vertex, they can be ruptured once the head is in the pelvis
What should be excluded between the delivery of the first and second twin in labour?
Cord prolapse
What should be done if the uterus doesn’t contract within a few minutes of delivering the first twin in labour?
Oxytocin infusion should be started
What is the purpose of starting an oxytocin infusion if the uterus doesn’t contract within the first few minutes after delivery of the first twin?
To ensure the uterus contracts to cause the baby to descend into the pelvis
What might need to be done during delivery of the second twin if the baby is breech?
In the absence of spontaneous descent, the attendant may need to hold the fetal foot and guide the foot and breech into pelvis to effect delivery
What is required if the attendant is going to hold the fetal foot and guide it into the pelvis during the delivery of the second twin?
It can be uncomfortable, and so adequate analgesia should be given
What should be done if fetal heart rate abnormalities occur during the delivery of the second twin?
Delivery should be expedited by forceps delivery or breech extraction, or rarely urgent C-section
When is emergency C-section to deliver the second twin required?
- When placenta seperates after delivery of first twin and tries to deliver before 2nd baby
- When baby cannot be delivered easily
Why is important to use oxytocic agents with the delivery of the second twin by labour?
As there is an increased risk of post-partum haemorrhage
What are the complications of labour in twin pregnancy?
- Locked-twin syndrome
- Complications associated with conjoined twins
Is locked-twin syndrome common?
No, it is very rare
When can locked-twin syndrome occur?
When the first baby is breech and the second is cephalic
How does locked-twin syndrome happen?
As the first twin descends during delivery, the twins lock chin to chin
When is locked-twin syndrome recognised?
Usually not recognised until delivery of part of the first twin is delivered
What is the prognosis of locked-twin syndrome?
Survival is unlikely unless as an urgent C-section is organised
How is locked-twin syndrome avoided?
Twins where ultrasound reveals that the first twin is presenting breech and the second by vertex should be delivered by elective C-section
How should conjoined twins identified by ultrasound be delivered?
C-section
What happens if unidentified conjoined twins are delivered vaginally?
Labour will usually obstruct
What % of perinatal mortality is associated with multiple pregnancy?
10%
What is the most common cause of perinatal death in multiple pregnancy?
Prematurity
What are second twins more likely to die from?
- Intrapartum asphyxia
- Cord prolapse
When does intrapartum asphyxia of the second twin occur?
After separation of the first twin
When might cord prolapse occur in multiple pregnancy?
May occur in association with malpresentation or a high presenting part when membranes are ruptured
